Antihunting means for control devices



June 7, 1949. I M, N. YA DENY 2,472,271

ANTIHUNTING MEANS FOR CONTROL DEVICES Filed Feb.- 26, 1944 3Sheets-Sheet 3 FIGQE 11" 1111/ 111i! I Ill/11A r- MCI-MY 'MYA RDA-NY 23'INVENTORA Q3? Mama ATTORNEY Patented June 7, 1949 UNITED STATES PATENTOFFICE ANTIHUNTING MEANS FOR CONTROL DEVICES 6 Claims.

My invention relates to improvements in antihunting means to be used inconjunction with control apparatus and systems for placing a load orobject in a predetermined or stopping position or in one of severalpredetermined positions. It relates more particularly to improvements inanti-hunting means for control apparatus comprising a movable controlelement and reversible drive means for the control element which drivemeans are rendered inoperative when the control element reaches apredetermined stopping position.

With control apparatus and systems of the type described, difficultieshave been encountered to secure an accurate and definite stopping of thecontrol member in its predetermined position. These oulties aresubstantially due to oscillations and continued movements of the drivemeans, preferably a motor, after the drive means have been renderedinoperative. Such oscillations and continued movements of the drivemeans tend to cause the control element to overrun its stopping positionand then to hunt for position thereby adversely affectin the accuracyoperation of the control apparatus.

A principal object or" my invention is to provide novel improvedanti-huntin means for sup-pressing, eliminating and absorbingoscillations and other continued movements of the drive means afterhaving been rendered inoperative.

Another object of my invention is to provide novel improved means forreducing the force of inertia affecting the drive means and causingcontinued movements and oscillations of the drive means after these havebeen rendered inoperative. I hereby reduce any ten ency of the controlelement to oscillate at its predetermined stopping position or to huntfor such position.

Another object of my invention are novel and improved means forsuppressing, eliminating and absorbing oscillations other continuedmovets of the e means after these have been rendered inc. retire byincluding a means be- '1 the drive means and the control element whichcauses the control element to move at lower spee than the drive meansupon a reversal of in its new direction at a reduced speed and can berapidly and conveniently stopped When reaching its stopping positionbefore having attained a high speed.

Another object of improved means for providing a limited frictionalinvention is novel and play between the control element and the drivemeans for absorbing and rendering harmless and inefiective oscillationsand continued movements of the drive means after these have beenrendered inoperative.

Another object of my invention are novel and improved means forproviding a limited play and a progressively increasing friction betweenthe control element and the drive means after these have been renderedinoperative.

Another object of my invention is a control apparatus comprising amovable control element driven by reversible drive means which arerendered inoperative when the control element reaches a predeterminedstopping position and a frictional clutch between the control elementand the drive means for causing limited play and progressivelyincreasing friction between the control element and the drive means upona reversal of the drive means.

Another object of my invention are novel and improved anti-hunting meansin which means for suppressing, eliminating and absorbing oscillationsand other continued movements of the drive means after having beenrendered inoperative are combined with and supplemented by means foryieldably retaining the control element in its predetermined or stoppingposition. I hereby accomplish that a control element reaching itsstopping position at low speed due to the effect of the means forsuppressing, eliminating and absorbing oscillations and other continuedmovements of the drive means is retained and rapidly stopped in itspredetermined stopping position by the retaining means when the drivemeans are rendered inoperative and are moving by inertia only.

Other and further objects and advantages of my invention will behereinafter set forth and the novel features thereof defined by theappended claims.

Referring to the drawings which illustrate several of variousembodiments of my invention but to which my invention is by no meansrestricted since the drawings are merely shown by way of illustrationand not by way of limitation:

Fig. 1 is a sectional plan View of a control apparatus of the type alsoknown under the trade-mark or trade name "Spot Tuner, includinganti-hunting according to my invention.

Fig. 2 is a sectional view of Fig. 1 taken along the line 2-2 of Fig. 1.

Fig. 3 is a fractional sectional view of Fig. 1 taken along line 33 ofFig.

Figs. 4, 5, and 6 are detailed views of parts or elements of the controlapparatus shown in Figs. 1 and 2.

Fig. '7 is a detailed view of a modification of a clutch to be used. inconjunction with the control apparatus shown in Figs. 1 and 2.

Figs. 8 and 9 are detailed views of another modification of a clutch tobe used in conjunction with the apparatus shown in Figs. 1 and 2.

Fig. 10 is a. sectional View of another modification of my invention,the apparatus shown in Fig. 10 being distinguished from the apparatusshown in Figs. 1 and 2 by the structure of the clutch used.

Figs. 11 to 16 are detailed views of friction discs used in a clutchaccording to Fig. 10

Fig. 17 is a detailed view of the driving member of the clutch accordingto Fig. 10;

Figs. 18 and 19 are a detailed plan and sectional view respectively ofanother element of the clutch according to Fig. 10.

Fig. 20 is a plan view of an assembly of discs used for the clutch shownin Fig. 10.

Fig. 21 is a circuit diagram of an electric control apparatus accordingto my invention, the diagram showing several circuits for placing auseful load in. one of several predetermined positions, the drivingmeans being shown as a series wound motor.

Fig. 22 shows a modification of the friction clutch shown inFigs. l and2' or 10.

Fig. 23 shows a sectional view of another modification of'a frictionclutch according to my invei'ltion.

Fig. 24 is a plan view of Fig. 23 showing the various friction elementsof the clutch in a certain relative position.

Fig. 25 is a perspective view of the clutch showing the various frictionelements of the clutch'in substantially the same relative position asFig. 24.

Fig. 26 shows a perspective view of one of the friction elements of theclutch.

Fig. 2'? shows a development of a friction element.

Fig. 28 isa plan view similar to Fig. 27 but showing the frictionelements in different relative positions.

Fig. 29 is aperspecti've view of the clutch corresponding to Fig. 28 andsimilar to Fig. 25 with the exceptibn' that direction of rotation isreversed; and

Fig. 30 is a sectional view of the gap between twoconducting segments onan enlarged scale.

The device shown in Figs. 1 to 6 comprises a shaft"! mounted in bearings(if and 62 supported by end plates 63 and 84. These end plates togetherwith postsor standards 5'6, 6'1 form a housing or frame for the controlapparatus. Shaft l carries contact members or contactors 8; '9' Thesecontactors are preferably made of resilient conducting material mountedon: shaft 1 either directly or by means of sleeves fill. They areaxially slidabl'e but secured against rotati'on by means of a flattenedsection as of shaft I or any other suitable means. Each contactor mayhave a' substantially triangular shape and carries a contact ball ispreferably made of chromium, tungsten, or other hard metal. In stead ofballs similar bodies of revolution such as cylinders-may be used. Thecontact member is shaped and arranged to bridge a gap separating" twoconducting members or segments preferably by a two point contact. Thegap itself may be shaped and. elevated as, for example, shown in Fig. 30and more fully-described in my Patent 2,342,711 and. copendingapplications, Serial No.

4 477,469, filed February 27, 1943, and Serial No. 490,767, filed June14, 1943, now abandoned. The elevation of the gap may also be one sidedas shown in my copending application Serial No. 522,062 filed February12, 1944.

The conducting members or segments designated by numerals i, 2 may havea semi-circular shape or. preferably the shape illustrated in Fig. 1.This figure shows an annular segment 5 having a substantially triangularrecess in which the substantially triangularly shaped segment 2 isplaced. Both segments are separated by a hen tral point or line such asgap 5. Each pair of segments is supported on an annular disc or ring 73made. of a suitable insulating material such as known under thetrade-mark Bakelite. The insulated discs" are rotatably supported incorresponding slots or grooves '85 provided in posts 65, 66, 61. Inorder to secure discs 73 in their positions in the slots or grooves,borings or holes 11- in alignment with grooves are provided in post 65"holes plungers or balls '12 are inserted. These balls are pressed bsprings 66' or other suitablemeans against the edges of discs 13,thereby pressing the discs against the bottoms of the grooves or slots'15 in posts 66- and 61 as shownin Fig. 1.

The 'o'uter segments l are secured to the upper side of. the annulardiscs 13 by rivets 8i screws or. similar means. The bottom side of eachan nular disc carries a ring 82 or similarly shaped element ofconducting material which is fastened to its disc by means of rivets,bolts, or screws &3. The rivets may also serve toconnect the innersegment 2 electrically to ring 82. :It is of course also possible toprovide'sepa'rate rivets or bolts for this purpose. Ihe segmentsv areconnected to the electric circuits of the apparatus by suitable meanssuch as a pair of tongues 85 and 86 respectively for each annular disc.segment I and fingers 8E rings 82. Fingers 85, 86 are separated byinsulators 8i and fastened to the housing: of the control apparatus byany suitable means. Screws 88-, 89 may be provided to holdthe fingersand the insulators together. In the embodiment illustrated in thedrawings the conducting segments are placed on the top side of the discsand the rings are fastened to the lower side. The reverse arrangement isof course also possible.

As will be explainedmore fully hereinafter and in connection with thedescription of the circuit diagram shown in Fig. 21, shaft 1 is drivenby suitable reversible driving means such as a reversible motor 209which will be operative in one or the other direction when a contactorengages one of the conducting segments and will be renderedinoperativeor stopped when a contactor reaches or bridges a gap. The relativepositions of the. annular discs and hence of the gaps can be adjusted byany suitable means, for example, by rotating the discs individually.Figs. 1 and 2 show suchv means to adjust the positions of the gaps forone: of the discs 13 in detail. A shaft is rotatably supported betweenend plates 63. and 65 and can be rotated by means of screws 94 shown inFig. 2. The shaft carries friction means, for example, an upper frictionwasher 31 and. a lower friction washer 98 which washers engage the edgeof the corresponding disc T3. Hence a rotation of shaft 95 will cause a.rotation of the. engaged. disc and with it of the gap separating theconducting members fastened to the disc. Inorder to secure a transportof the disc, the engaging surfaces of the friction wash- Fingers 85engage ers may be slightly knurled. I found it advantageous to fit oneof the friction Washers, for example, the upper washer, rigidly on theshaft and the lower washer slidably and to provide spring means such asa helical spring 99 pressing washer 98 against the disc. The tension ofthis spring is chosen so that a disc can be accurately adjusted byrotating shaft 95. Resilient brakes may be provided which engage thelower portion of shaft 95 frictionally to prevent an unintentionalrotation of the shaft causing a displacement of the disc and of the gapdue to the pressure of the contactor engaging the conducting memberscarried by the disc.

It is of great importance to prevent oscillations or hunting of thedrive means after these have been rendered inoperative in response to acontactor reaching or bridging a gap. I have found that due to inertiathe motor will not stop abruptly after having be-In rendered inoperativebut will continue to move in its original direction, thus forcing thecontactor out of the gap. Assuming, for example, that the contactor hasmoved over segment I and engaged gap 5, thus bridging segments I and 2in which position the motor is rendered inoperative. As a result of thelimited continued movement of the motor due to inertia, the contactorwill be forced out of the gap and will now engage segment 2 only.Consequently, the motor will be restarted immediately in reverseddirection as previously explained and more fully explained hereinafterand move the contactor toward the gap. Due to the momentum of the motor,the contactor will again overrun the gap whereupon the motor is againrestarted in reversed direction. This cycle may repeat itself manytimes, in other words, contactor and motor will oscillate near the gapand hunt for the gap. Such hunting and oscillations tend to affect theoperation and accuracy of the control apparatus as explained more fullyin my Patent No. 2,342,717. According to my invention, I avoid suchhunting and oscillations by providing anti-hunting means forsuppressing, eliminating and absorbing oscillations and other continuedmovements of the drive means after these have been rendered inoperative.

According to my invention this result can be accomplished by reducingthe force of inertia affecting the drive means and causing continuedmovements and oscillations of the drive means after these have beenrendered inoperative, for example, by providing means causing thecontrol element to resume its movement at a comparatively low speedafter a reversal of the drive means even though the driven means resumetheir movement at a higher speed. As a result the inertia of the controlelement when reaching its stopping position will be rather low and thecontrol element can be rapidly and conveniently stopped. According to apreferred embodiment of my invention I provide a certain limited amountof frictional play in the operative connection between the shaft 1 andthe driving motor. This frictional play will prevent the motor to gathersuflicient momentum and speed when reversed near the gap so that thecontactor reapproaches the gap at a slow speed. Consequently, the motorwill rapidly come to a standstill leaving the contactor in its gapbridging position. The effect of the frictional play can be enhanced orsupplemented by providing frictional resistance in the gap itself, forexample, by raising the edges of the gap as previously mentioned. Suchraised gap will yieldably retain a contactor reaching the gap withsufficient torque to overcome the frictional resistance of the operativeconnection while the latter absorbs the remaining inertia of the motor.

A suitable arrangement for this purpose is shown in Figs. 1, 2, 4, 5 and6 in detail.

The shaft III) of the motor 2% is coupled to a rotatable shaft I IImounted in bearings II2 by gears I I3, or any other suitable means.Shaft III carries a worm H4 ngaging a worm gear I IS on the periphery ofa disc I I6. However, any other suitable drive between motor 20d anddisc I I6 can be provided. Disc H6 is rotatably mounted on a bushing orsleeve I II rotatable on shaft I and cooperates with friction discs I20,I2I and I22. Discs I20, I72! and I22 are mounted on shaft I, disc IZIbeing rotatably mounted thereon and disc I22 being rotatably mounted ona bushing which, in turn. is rotatably mounted on the shaft. Disc I26 isprovided with elongated recesses or slots i223, I24, disc iZI withelongated recesses or slots I25, I25 and disc I22 with an elongated slotor recess itl. Recesses I24, I25 and I21 are engaged by a pin ISiextending from a disc I3I keyed to shaft I. Recesses I23 and I26 areengaged by a second pin I32 extending from disc I22. In order toincrease the frictional resistance between the discs, spring-s I33 maybe provided between some or all of the friction discs. Differentlystrong springs may be used to obtain varying friction between successivediscs. It is also possible to use a single spring to compress thefriction discs that are slidable on shaft I. Disc I22 and motor drivendisc IIB are frictionally coupled by a spring I34 or by friction betweenthe discs themselves. Instead of three friction discs as shown in thedrawing, any other suitable number of discs can of course be used. Thefriction coupling oper ates as follows:

When motor 20!] rotates disc H6 in one direction, all frictional discsof the drive will be shifted to one side, the drive being effected bypins I3il, I32 engaging the corresponding edges of all the discs at theslots 0r recesses and transmitting drive through the shaft I, throughthe gear ISI. Upon reversal of the rotation of the motor, however, thepins move away from the engaged edges, the rotation being thentransmitted by the friction between the discs. Due to the progressivelyincreasing length of the recesses, the friction discs are successivelyconnected for direct drive. After the first disc slides into a positionin which the driving pin engages the edge of its recess, the second discwill be also engaged and will slide together with the first disc untilthe third disc is engaged, and so on, depending upon the number offrictional discs. The amount of frictional work between the discs andthe springs will absorb oscillations of the motor completely or at leastsubstantially before reaching shaft I. Furthermore, the clutch will notimmediately transmit the fuil speed of the motor to shaft I and hence tothe contactors due to the slippage between the frictional elements ofthe clutch when the motor resumes its rotation after a reversal.Consequently, shaft I will begin to rotate at a substantially lowerspeed than the motor and the contactors will approach the gap withcorrespondingly reduced inertia and the motor will be again renderedinoperative. Due to the low speed of the contactor, its tendency tooverrun the gap will be very slight and the contactor will be retainedin the gap by the effect of the elevated edges of the. gap and will bebrought rapidly to a final stop.

A modified frictional clutch or coupling using internal friction isshown in Fig. 7. This coupling Comprises two halves, MD, MI providedwith lugs or projections H32, I43 passing through corresponding holes ina flexible ring I44 made of an imperfectly elastic material such as arubber composition. This ring will be elastically deformed by torsionalforces as shown in dotted lines in Fig. l. The internal friction ofthis-deformation will absorb oscillations of the motor at least to asubstantial extent.

Another type of a frictional clutch or coupling using internal frictionis shown in Figs. 8 and 9. This coupling comprises two halves I45, I46a-rrangedat right angles to each other and connected by springs Hill. Inorder to damp the spring oscillations, imperfectly elastic rods M8 maybeprovided.

'Shaft 'I' may be coupled to a shaft I35 of a useful load such as tuningcondenser by gears such a's'ISG, I37. In order to maintain the accuracyof the movements transmitted. from shaft 7 to shaft I35, a clock springI3 8 may be placed between shaft I35 and a bearing I39 for this shaft.This spring is held under constant tension thus maintaining the gearingteeth in constant contact in the same direction, thereby eliminating any"play in the gearing. Gears I36, I31 may also be used to increase theresistance of the contactor movements in one direction thereby causing atendency of the shaft to overrun in one direction and to stop on itsreturn movement, thus increasing the accuracy of the device.

Means may also be provided for a manual rotation of shaft TI. Accordingto the embodiment illustrated in Figs. 1 and 2, the periphery of discI3I is provided with teeth I50. These teeth are engaged by a pinion I5Ikeyed to a shaft I52 supported by end plates I53 and 64. A thumbhead I53may be provided at the end of shaft I52 to facilitate rotation of shaftI52. Instead of a gear drive as shown in Figs. 1 and 2, another suitabledrive such as a friction drive can be employed. The worm gear drive III, III; being irreversible, the clutch assembly will slide over thespring I34 when the manual gears are rotated, leaving the motorstationary. The spring I34 connecting the worm gear I I6 with the clutchmade for this purpose is substantially stronger than the springs I33 sothat there is normally no slippage in the worm gear.

Figs. to show another and preferred modification of a coupling or clutchpermitting a limited progressive frictional play between shaft I and themotor driving this shaft.

The clutch is illustrated in conjunction with a control apparatussimilar to the one shown in Figs. 1 and 2. It comprises a bushing orsleeve I60 loosely mounted on shaft I and abutting with its lower flangeIIiI against a collar I162 of shaft 1. The bushing carries the gearwheel I'IIB" engaged by worm IM and a friction disc I63 from whichextends a pin Itd. Gear wheel H6 and disc I63 are pressed by a springI65 against the upper flange I66 of bushing Itl) thereby forming a.self-contained unit and a frictional coupling between gear wheel H6 anddisc I63. and also between these two elements and the bushing. Gearwheel H6 and disc I 63 form the driving element of the frictionalclutch. The driven ele-v ment of this clutch comprises a disc I61 fromwhich extends a pin I68. This, disc is keyed to shaft 1' by means of aflattened surface IE9 or othersuitable means and fastened byrivets I10.-or similar means to gear wheel I3I engaged by; pinion I5I. Gear wheelItI may be provided with,

a curved guiding slot I'II extending over approximately 180 degrees andengaged by pin I64. The driving element and the driven element of the"clutch are frictionally coupled by a plurality of" These discstionarydisc I12 has two noses or lugs I13 and. I14 spa'ced sufficiently to forma recess to be, engaged by one of the pins I64, I68, for example, bypin:

I68. The discs of the other set hereinafter referred to as movable discsshapes. Each of the movable discs, three of which are shown in Figs. 12,14 and 15 and desigw nated by numerals H5, H6 and Ill, has twoelongatedrecesses. One of the elongated'recesses designated by numeral I18 hasthe same length for all movable discs and extends preferably overapproximately 180. second recess is difierent for each movable-disc; Therecesses are separated by narrow lugs I16. Disc I'I't has a secondrecess I'I9, disc I'HS, a second recess I89 and'disc Ill andasecot1drrecess ItI. It will be noted that the recesseszl'l9, 88d and MIare of gradually extending lengths; Stationary and movable discs areassembled so that pin Hi8 engages the recesses between noses I 73 andI'M of all stationary discs and, also the recesses IIil of all movablediscs and that pin I84 engages recesses I79, I80, Id! of the movable.

discs and passes all stationary discs outside the recesses formed bynoses Ilt, IM. One-stationary disc is always sandwiched between twomovable discs.

Fig. 20 shows a plan view of an assembly composed of a stationary discI12, movable disc I 15,

a second stationary disc I72, movable disc I l'fi, a

but permits movements of the movable discs within a range of 180corresponding to thelength of recesses IN. The possible relativemovements of the movable discs are determined by the lengths of theirrecesses I18, Hit and Id! engaged by pin "I63.

It will be understood from the previous-description that any suitablenumber of stationary and movable discs may be used and that each pin maycontrol either the stationary or the movable discs.

An assembly of discs such as shown in Fig. '20 is inserted between thedriving and the driven element of the clutch and compressed by a springI85 preferably placed between disc I63 and the bottom disc ill of theassembly of discs. Spring I85 have upward and downward bent prongs I86and It'll pressing against discs I63 and Ill respectively at itsperiphery, thereby obtaining a greater frictional torque. (Figs. 18 and19).

I have found it advantageous to arrange the spring so that the pressureexerted by it is directed substantially against the outer parts of discsI83 and Ill.

The operation of the clutch is as follows:

When gear wheel IIE' is rotated by worm II' t',-

disc it'd will rotate together with gear wheel I'Ifi. Gear wheel H6 anddisc I53 may be considered as rigidly coupled in this connection, thefriction between these discs being so great that they will not moverelatively to each other unless the-con-= have different The length ofthe- 9 tactors 8, 9 are manually moved as previously described.

Assuming now that gear wheel I I6 is rotated in the direction indicatedby an arrow shown in Fig. 2G and that all movable discs are in aposition in which all the left edges (as viewed in Figs. 12, 14 and 15)of projection I it" are engaged by the pin I54, which also engages discl3l at the end of slot I'll. All the intermediate discs I12 are engagedby the pin H33 extending from the disc It! and, consequently, rigidlyconnected to the shaft l. The other lugs I16 are spread out as shown inFig. 20. The clutch is then rigidly connected for transmitting to fulldriving torque. When the motor rotation is reversed, however, the pinI64 will leave the end of the slot Ill and will move until the other endof the slot is reached and the solid driving connection isreestablished. While pin I 64 is moving in the slot, torque istransmitted through the frictional plates as follows (Fig. 20) Pin 164,after leaving the left edges of projections I16", will reach the firstlug I16, causing the corresponding disc I75 to rotate until the next lugH6 is reached, when the next disc Ilt will also turn; and, finally, thethird lug I78 will be engaged, and all three discs will be rotated untilthe pin I54 reaches the end of the slot I7 I, as was mentioned above.

With the reversal of the rotation the pin I64 will at first move thedisc I15 until disc I I6 is reached, and so on, moving progressivelyincreasing the number of discs. The discs, moving relatively of theadjacent stationary discs I12, will develop certain frictional work,absorbing part of the oscillations and movements of the motor after themotor has been rendered inoperative.

As it is apparent from the previous specification, the friction discs ofthe clutch are made successively efiective, thus progressivelyincreasing the total frictional work to be overcome by the oscillationsand movements of the motor due to inertia. Furthermore, the clutch willnot immediately transmit the full speed of the motor to shaft I andhence to the contactors due to the slippage between the frictionalelements of the clutch when the motor resumes its rotation after areversal. Consequently, shaft 1 will begin to rotate at a substantiallylower speed than the motor and the contactors will approach the gap withcorrespondingly reduced inertia and the motor will be again renderedinoperative. Due to the low speed of the contactor, its tendency tooverrun the gap will be very slight and the contactor will be retainedin the gap by the eifect of the elevated edges of the gap and will bebrought rapidly to a final stop. I have found that the use of africtional clutch as previously described will result in a rapid andeffective stoppins of the motor movements and oscillations after themotor has been rendered inoperative.

The circuit diagram shown in Fig. 21 can be advantageously used inconnection with and for the operation of a control apparatus accordingto my invention. However, it should be understood that a controlapparatus according to the invention can be used and operated inconnection with any other suitable circuit system.

The circuit diagram shown in Fig. 21 comprises one or more pairs ofconducting members I, 2, 3, 4, etc. each pair being separated by aneutral point 5, 6 such as a gap. The driving shaft 1 of the apparatusis rotatably supported on the common axis of the segments and mountscontactors or contact members 8, 9 slidably engaging the segments asexplained more fully in connection with the previous figures. Thecontact point or element at the end of each contactor is suflicientlylarge to bridge an engaged gap thus electrically connecting theconducting members separated by the gap. Shaft "I can be revolved by anysuitable reversible driving means. In the circuit system shown in Fig.21, the armature of reversible electric motor 2% is operativelyconnected to shaft i. Fig. 21 illustrates a series wound motor havingseries field windings MI, 282. However, it should be understood that anyother suitable type of motor such as a shunt wound or induction motorcan be employed.

Segment I is connected to a relay coil 203 through a lead and segment 2to a second relay coil through a lead 206. Segment 3 is connected tocoil through a lead 25! and segment i to coil 2% through a lead 208.Leads 2e41, include switches 209, 2H] respectively, simultaneouslycontrolled. by a common handle 2H, Leads 29?, 2% include switches 2E2,2I3 respectively, simultaneously controlled by a common handle 2%.Contactor 8 is connected to one terminal 215 of a source of currentthrough a lead 2 it and contactor 9 is connected to terminal 2Z5 througha lead 2i! and lead 2H5. Coils 203 and 235 are connected to the secondterminal 2I8 through a common lead 219 and a lead 220. Coil 2&3 controlsa pivotal arm 22I engaging a contact point 222 in its released positionand a contact point 223 in its attracted position. Coil 285 controls apivotal arm 22d engaging a contact point 225 in its released positionand a contact point 226 in its attracted position. Arms 22I and 224 areconnected by a lead 221. Contact points 223 and 228 are connected tolead 220 and contact points 222 and 225 to one of the ends of fieldwindings till, 262 respectively. The other ends of these field windingsare connected to one end of the armature of motor 2% through a commonlead 228. The other end of the armature is connected to terminal 2I5through a lead 229. Assuming now that switches 20%! and 2H) are closedand that contactor 8 engages segment 2, then a circuit for relay coil295 is closed from terminal 2i5 through lead 2W, contactor 8, segment 2,switch 2H3, lead 2%, relay coil 295, lead 2I9 and lead 220 to terminal 2I8. Coil 205 will attract its arm 224 which will engage contact point226, thus closing a circuit for the motor from terminal 2I8 through lead220, point 226, arm 224, lead 22?, arm 22!, point 222, field winding 2!,armature of motor 2% and lead 229 to terminal 2 I5. The motor willrotate in a definite direction and move contactor 8 toward gap 5. Whencontactor 8 engages segment I, similar circuits for relay coil 263, themotor and field winding 202 are closed causing a rotation of the motorin the reversed direction.

As soon as contactor 8 engages and bridges gap 5, both relays areenergized and attract their arms thus disconnecting the motor and itsfield windings from the source of current. If the relays are arranged tobe both deenergized upon a contactor bridging a gap, the field windingsare short circuited through lead 221.

It will be noted from the drawings that the motor will be restarted inreversed direction if the contactor overruns the gap due to inertia ofthe motor and again rendered inoperative when the gap is bridged againby the contactor. The oscillations and movements of the motor causedhereby will be absorbed and suppressed by the previously describedanti-hunting means.

The modification shown in Fig. 22 discloses 11 means'for coupling thedriving element and the driven element of the clutch sufficiently.rigidly to prevent a rotation of the driven element in either directionwith. or without substantial. frictional play. Such an arrangement isadvantage-. ous under certain circumstances, i. e. when gear wheel H6normally driven-by the'motor is to be rotated by a worm 230. manualyvdriven by a shaft 23! having a thumbhead.

This purpose can be accomplished. by: providing electromagneticmeanswhichif energized urge axially slidable'gearwheel: l3! toward gear wheellid, thus compressing the friction discs of the clutch and prohibiting africtional play or slippage upon reversal.

These electromagnetic means comprise an annular core 232 fastened togear wheel I I6 and coil 233, whichmay. be stationary and may beconnected to a source of current 25'! and a control switch 258.

The modified clutch shown in-Figs."23 to=29 comprises an outershell-235attached to the-drive shaft i, for example; by a bushing'236-and a pin 33?. Rotation. of the-:motor is transmitted by a worm gear233 rigidly-fastened to a sleeve 239 freely rotating on the shaft #1 andretained in its axial positionbya collar 240. A-pin 234' extends fromthe shell 23:5. toward-.thesleeve-239. The pin engages slots formedbetweenlugs 2:45 on concentric frictional -sleeves flll' positioned:be-. tween the sleeve 23 9. and the outer-shell 235. The sleeves. are:split lengthwise (see'Fig. 26-)- and maybe slightly deformed from thetrue cylindrical shape to increase their resilient frictional engagementwith the other sleeves. or finger 246 extends fromstheinner-sleeve 23-9-beyond the outer shell 2'35isand engages a recess 2 H which limits thepossible:relativemotion betweenthe. outer shell 23.5 .keyed tosh-aft land the inner sleeve 2-39 fastened to gear 238;

Additional frictional sleeves: 248, 249, fill-having .slots of varyingwi'dth between lugs-251,252, 253v and 254 are. placed betweenthesleeves-"241. The lugs. 25.1 are relatively narrow while the lugs 25.2,253, 254- arerel-atively wide and are of dif ferent width for differentsleeves. The distance between the lugs-at. oneside is the same for allsleevesand approximately equals the length of the slot or recess 247.;while the: distance betweenthe lugs. at the otherside:progressivelyvaries for different sleeves. I

During-the rotationof-the motor, the pin 24-5 engages one or the othershoulder at the 'end of the recess 241, depending on thedirectionofrotation. Fig. 25-shoWs the position of-the pin 246 for clockwiserotationof theshaft 'l. The pin 2% gathers in front oritwallnarrow lugs25!, the long lugs being distributed inthe space limited by the recess24! as shownind ig. 25.

Upon reversal of themotor rotation, the pin 24-6 leaves the shoulderofthe recess 241, moving in a counterclockwise direction. It engages atfirst the longest lug 252-; "causing the sleeve 248 to rotate betweenthe adjacent sleeves 241' and also moving forward the corresponding lug25L Upon completion of' the first movement, the pin 246 engages also thenext lug 253 of the sleeve 249, causing the'latter to rotate with thesleeve 248 and moving the corresponding short lug 25] also forward. Thethirdsleeve .250 is picked up in the same manner,.the.r orce offrictionprogressively increasing untilth pin 24.6. abuts the other shoulder inthe recess 241. as shown in Fig. 29. All the long lugs will b the A pingathered in front of the pin 2% and the short lugs will be spaced in therecess 241.

With the next reversal of rotation, the pin 2% will successively pick upthe short lugs, can..- ing the corresponding sleeves to rotate until theposition of Fig. 25 is reached again.

The operation and effect of the clutch shown in Figs. 23 to 29 issubstantially similar to the one described in connection with Figs. 1, 2and 10.

I have found that in order to obtain substantially the same frictionbetween the friction elements at all times it is desirable to place asuitable lubricant between the frictional surfaces. The lubricantreduces friction to a certain extent, requiring a somewhat greaterspring tension, but it helps to maintain the surfaces smooth, preventingtheir abrasion or scoring.

For operation at low temperatures such as, for instance, use with radiocontrol devices on airplanes, I prefer to employ a commercial greaseespecially made for low temperatures, such as Beacon -M 285 which,according to my experience operates satisfactorily in my clutch attempera tures as low as 55 C.

It will be understood that various features and principles of each ofthe. embodiments of the invention above described or referred to -may beutilized or substituted in the other embodiments.

While the inventionhas been described in.-de.- tall with respect tocertain particular preferred examples, it will be understood by thoseskilled in the art after understanding the inventionthat various changesand further modifications may be made without departing from the spiritand scope of the invention, a d it is intended therefore in the appendedclaims to cover all such changes and modifications.

What is claimed as new and desired to beseouredby Letters Patent is:

l. A frictional clutchinterposed between a re, V-ersible driving memberand a driven member, comprising, in combination, a rotatably mountedclutch element driven by the said drivingmemher, a second clutch elementsecured to. rotate with the said driven member and provided with anarcuate slot and a stud, said-clutch element of thedrivingmemberbeingprovided with a stud slidably received in the saidarcuate slot of the clutch element of the driven member, a plurality ofrotatably mounted discsinterposed between thesaid two clutch elements.and connected to the said stud of the clutch element of the drivenmember, a second plurality of rotatably'mounted discs likewise disposedbetween the said two. clutch elements and alternately spaced relative tothe first said plurality of discs, each, of the discs of the said secondplurality havinga pair of spaced projections adapted to receive thesaid. stud of the clutch element of the driving mem ber between theirfacing edges, the arcuate distancebetween the said projections beingdifferent in individual ones of the plurality of discs and; less thanthe length of the said arcuate slot. whereby the said driving memberpositively drives the. driven member by abutment of its said stud withthe anteriorend of the said arcuate slot, the anterior projections ofthe second said pluralities of discs being aligned. through entrainmentby the last-mentioned stud to cause theposterior projectionsto bestaggered at different distances from the; said aligned anteriorprojections, and spring means to apply friction between the two. saidpluralities of alternately spaced discs whereby upon reversal ofdirection 13 of the said driving member, its said stud willprogressively abut the said staggered projections to frictionally drivethe said driven member with correspondingly increased torque, the saidstud thereafter positively driving by abutment with the other end of thesaid arcuate slot.

2. A frictional clutch interposed between a reversible driving memberand a, driven member, comprising, in combination, a rotatably mountedclutch element driven by the said driving member, a clutch elementsecured to rotate with the said driven member and provided with a pairof spaced stops, said clutch element of the driving member beingprovided with a stud abuttable with the said pair of spaced stops of theclutch element of the driven member, a plurality of discs interposedbetween the said two clutch elements secured to rotate with the drivenmember, a second plurality of rotatably mounted discs likewise disposedbetween i'he said two clutch elements and alternately spaced relative tothe first said plurality of discs, each of the discs of the said secondplurality having a pair of spaced projections adapted to abut the saidstud, the arcuate distance between the said projections being differentin individual ones of the plurality of discs and less than the spacebetween the said pair of stops whereby the said driving memberpositively drives the driven member through abutment of its said studwith the anterior one of the said pair of stops, the anteriorprojections of the second said pluralities of discs being alignedthrough entrainment by the said stud to cause the posterior projectionsto be staggered at different distances from the said stud, and springmeans to apply friction between the two said pluralities of alternatelyspaced discs whereby upon reversal of direction of the said drivingmember, its said stud will progressively abut the said staggeredprojections to frictionally drive the said driven member withcorresponding increased torque, the said stud thereafter positivelydriving by abutment with the other stop.

3. A frictional clutch interposed between a reversible driving memberand a driven member, comprising, in combination, a stud secured to thesaid driving member, the said driven member having an arcuate slot toreceive the said stud and being provided with a second stud, a pluralityof rotatably mounted discs interposed between the said two members andconnected to the said stud of the driven member, a second plurality ofrotatably mounted discs likewise disposed between the said two membersand alternately spaced relative to the first said plurality of discs,each of the discs of the said second plurality having a pair of spacedprojections adapted to receive the said stud of the driving memberbetween their facing edges, the arcuate distance between the said facingedges of the projections being different in individual ones of theplurality of discs and less than the length of the said arcuate slotwhereby the said driving member positively drives the driven member byabutment of its said stud with the anterior end of the said arcuateslot, the anterior projections of the second said pluralities of discbeing aligned through entrainment by said stud to cause the posteriorprojections to be staggered at different distances from the said stud,and spring means to apply friction between the two said pluralities ofalternately spaced discs whereby upon reversal of direction of the saiddriving member, its said stud will progressively abut the said staggeredprojections to frictionally drive the said driven member withcorrespondingly increased torque, the said stud thereafter positivelydriving by abutment with the other end of the said arcuate slot.

4. A frictional clutch interposed between a reversible driving memberand a driven member, comprising, in combination, a pair of spaced stopssecured to one of the said members, a stud provided on the other memberand abuttable with the said pair of spaced stops, a plurality of discsinterposed between the said members and secured to rotate with onethereof, a second plurality of rotatably mounted discs likewise disposedbetween the said two members and alternately spaced relative to thefirst said plurality of discs, each of the discs of the said secondplurality having a pair of snaced projections adapted to abut the saidstud, the arcuate distance between the said projections being differentin individual ones of the plurality of discs and less than the spacebetween the said pair of stops whereby the said driving memberpositively drives the driven member through abutment of the said studwith the anterior one of the said pair of stops, the anteriorprojections of the second said pluralities of discs being aligned by thesaid abutment between the said stud and the anterior stop to cause theposterior projections to be disposed at diiferent distances from thesaid stud, whereby upon reversal of direction of the said drivingmember, the said abutment between the said staggered projections of thesaid stud frictionally drives the driven member with correspondinglyincreased torque and the subsequent abutment between the said stud andthe anterior stop positively drives the driven member.

5. In apparatus for moving a load to desired positions, in combination,a pair of relatively movable members, one of the members having a pairof conducting elements separated by a gap, and the other member having acontact arm engageable therewith, a reversible motor for moving theload, one of the members being selectively pre-set to cause displacementbetween the said contact arm and gap and engagement with one of theconducting elements to rotate the motor in the desired direction, onemember of the said pair being operatively connected to the said loadmotor, a frictional clutch interposed between the said movable memberand the said motor, said frictional clutch comprising a pair of spacedstops secured to rotate with the said movable member, a plurality ofelements each provided with a pair of spaced stops, the distance betweenthe stops increasing with successive ones of the said elements, and astud rotatable by the said motor and receivable in the spaces of thesaid stops of the plurality of elements and in the space between thesaid pair of stops of the said movable member, the said elements beingin frictional engagement with each other and with the said movablemember, the said load motor positively driving the said movable memberby abutment of the said stud with the anterior one of the said pair ofstops of the movable member, the anterior stops of the said plurality ofelements being aligned by the said abutment between the said stud andsaid anterior stop to cause the posterior stops to be staggered atdifferent distances from the said stud, said movable member being movedin a direction to restore alignment between the said gap and contactarm, the said movable member overrunning the gap to engage with theanterior conducting element to cause reversal of motor rotation toreturn the movable member toward the gap, detent means to hold the saidmember at the tartan gap, said movable member being returned:Hoyt-rictional drive and with progressively increased torque as the saidstud sequentially abuts the said staggered stops, said motor *continuingiits movement by inertia after the said restored alignment of gapand with the contact arm held at the-gap.

6. In apparatus for moving a load to desired positions, in combination,a pair of relatively movable members, one of the members having a pairof conducting elements separated-bya gap, and the other member having acontact'armiengageable therewith, a reversible motor for :moving theload, one of the members being selectively pre-set to cause displacementbetween the said contact arm and gap and engagement of contact arm withone of the conducting elements to rotate the motor in the desireddirection, one member of the said pair being 'operatively connected tothe said load motor for rotation in a direction to restore alignmentbetween said gap and contact arm, the said movable member overrunningthe gap to engage withtheanterior conducting element to cause reversalof motor rotae tion, a frictional clutch interposed between the saidmovable member and the said motor, said clutch comprising adrivingelement coupled with said motor, positive coupling means onsaiddriving element, and a plurality of relatively movable driven elements.including one driven element coupled with said movable member, saiddriven elements being in frictional engagementwithione another, at leastsome of said driven elements being provided with formations cooperating,with 16 said positive coupling means for successive ,en trainmentthereby, with said one e'lementz'l'astren trainable so as to return thesaid movable :member towards the gap stepped increments of torque,v anddetent means to hold the said creturned movablemeinber at thel gap,motor rotation continuing by inertia after the saidrestored alignment ofgap and contact arm deeene'rg-izes the motor with the said movablemember held at the. .gap.

rMICI-IEL YARDENY.

REFERENCES CITED The following references {are of record in .fthe

file of this patent:

UNITED ST ES ATENT Number Name Date 950,290 Hughes Feb. 22, 19101,181,053 Anderson Apr525, 191-6 1,282,786 Entz Oct. 29, 1918 1,425,025Sc-h'afly Aug. 8, 1922 1,425,305 White Au=g.'-8, 1922 1,550,779Carpenter Au 25, 1925 1,557,525 'Hanson Oct. 13, 1925 2,094,777 EllingerOct. 5, 193 7 2,33%;980 Branson Nov. 9, 1943 2,342,717 Yardeny Feb-2 9,I944 2,360,157 Olson Oct, '10, 1944 FOREIGN PATENTS Number Country Date501,273 Great Britain Feb; 23, 1939

